The present paper continues the investigation started in Part I. The basic turbine stage remains the same as in Part I (an axial turbine stage with axisymmetric nozzles and mean diameter 103.5 mm). The numerical simulation method used in Part I was corrected by adding analytical correlation for disc friction losses. This approach was validated on the base of the experimental data for a geometrically close turbine. Variation of the radial velocity component at the rotor inlet was proposed as a new modification compared with Part I. The mathematical formulations of the rotor blade sweep and radial velocity component at the rotor inlet were proposed. The new modifications of the baseline were provided to establish the effects of the rotor blade sweep, velocity radial component at the rotor inlet and hub endwall contouring separately. The using of backward swept rotor blades together with the positive cinematic lean provided efficiency increasing up to 2.9% at the design conditions. It was also established that absence of a velocity radial component at the rotor inlet in the model with backward swept blades leads decreasing of the turbine performance. Axisymmetric hub contouring provided up to 1.9% efficiency growth at the part-load operation.
Organic Rankine Cycle (ORC) thermodynamic optimization is of critical importance while developing new plants. Optimization procedures may be imed at the highest efficiency as well as cost or sizing minimization. Optimization process is generally carried out for plant nominal rating. At the same time, part-load operation has to be carefully considered in case of waste heat recovery from flue gases coming from internal combustion engines or gas turbines. Gas mass flow and temperature variations are specific to this application, significantly influencing ORC plant performance. Secure prediction of part-load operation is of particular importance for assessment of plant power output, providing stability and safety and utilizing proper control strategy. In this paper design and off-design cycle simulation model is proposed. Off-design performance of the ORC cycle recovering waste heat from gas turbine unit installed at gas compressor station is considered. Major factors affecting system performance are outlined.
This paper presents the results of an aerodynamic analysis of a small-scaled transonic centrifugal compressor for micro turbojet engine (TJE) applications. The analysis was conducted using a CFD model validated by experimental data collected for the gaged JetCat P200-RX micro-TJE. The loss coefficients of the impeller, vaned diffuser and deswirler were estimated for 4 design points corresponding to 70%, 80%, 90% and 100% rotation speeds to perform the loss balance diagram. The flow angle spanwise variation demonstrated an intensive flow separation zone at the top 25% of the vaned diffuser span due to the pressure shock appearance. It was shown that the main source of the losses in the investigated compressor is the deswirler due to non-optimal flow turning conditions. The diffuser loss coefficient was estimated as 0.18 at the compressor full load.
Turboexpander generation technology is a promising solution for both CO2 emission reduction and providing autonomous auxiliary power for gas letdown stations and some technological processes. Nevertheless, its further development faces challenges to date due to several major restrictions: 1. long payback period of plants with conventional turbines; 2. significant annual fluctuations of gas inlet parameters; 3. high demands of conventional turbines for working fluid cleanliness. In order to address the abovementioned issues bladeless centrifugal reaction turbine may be introduced for turboexpander systems within power range up to 350 kWt. This turbine is a variation of so-called Segner wheel known for centuries. Its efficiency is lower comparing with the conventional rotary machines, but remains appropriate within the specific conditions of turboexpander application. Having proposed a conceptual design of a turbine the paper then highlights main features of its aerodynamics and kinematics. A comparison of the proposed turbine and axial transonic one is carried out within a wide range of pressure ratios as typical operating conditions. A centrifugal turbine advantage is highlighted which is an ability to generate comparable power as conventional ones while having lower cost and higher mud and erosion resistance.
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